Email Not Sending: Complete Troubleshooting Checklist

The Checklist

Work through these in order. Stop at the first failure.

1. Is the Service Up?

• Check your ESP's status page (e.g., status.sendgrid.com, status.mailgun.com)
• If the service is down, wait. Nothing you can do.

2. Is Your Account Active?

• Log into your ESP dashboard
• Check for suspension notices, billing issues, or limit warnings
• Verify payment method is current
• Check if you've exceeded your plan's sending limit

3. Are Your DNS Records Intact?

• Check SPF record: dig TXT yourdomain.com or use MXToolbox
• Check DKIM records: verify selectors are still published
• Check MX records: ensure they point to the right servers
• Common cause: someone accidentally deleted or modified DNS records

4. Are SMTP Credentials Correct?

• Verify host, port, username, and password match your ESP's settings
• Check if API keys were rotated or expired
• For GoHighLevel: re-enter SMTP credentials if your provider changed anything

5. Are You Rate Limited?

• Check your ESP's sending rate limits
• GoHighLevel sends everything at once — check if you exceeded hourly limits
• Some providers throttle new accounts or accounts with recent reputation issues

6. Were You Auto-Suspended?

• ESPs automatically suspend accounts that exceed bounce rate thresholds (~10%) or spam complaint thresholds (~0.5%)
• Check your ESP's logs for suspension notices
• If suspended: clean your list, contact support, request reinstatement

7. Is Your Domain/IP Blacklisted?

• Check MXToolbox Blacklist → enter your sending IP
• A blacklisted IP can cause all email to be rejected
• If blacklisted: request delisting, fix root cause

8. For Self-Hosted: Server Health

• Is the server running? systemctl status postfix or check Docker containers
• Is port 25/587 open? telnet mail.yourdomain.com 587
• Is the SSL certificate valid? Expired certs = TLS failures
• Check mail logs: /var/log/mail.log or Mailcow's log viewer

Practitioner note: The most common "email stopped sending" cause I see: billing failure. Credit card expired, payment declined silently, ESP suspended the account. Check billing first — it's the fastest diagnosis.

Practitioner note: For GoHighLevel specifically: if SMTP suddenly stops working, check if your SMTP provider rotated credentials or changed API key requirements. SendGrid periodically requires API key rotation for security. If your old key was invalidated, GHL can't authenticate.

If you've worked through this checklist and still can't identify the issue, schedule a consultation — I'll diagnose the infrastructure failure and get your email sending again.

Sources

• SendGrid: Status Page
• Mailgun: Status Page
• MXToolbox: SMTP Diagnostics

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v1.0 · March 2026